1. Field of the Invention
The present invention relates to artificial hair such as that used to dolls, wigs, hairpieces, or an artificial hair for direct prosthetic implantation into a human body, and more particularly, to matted (delustered) artificial hair having an appearance and gloss extremely similar to that of natural human hair, and a process for producing the same.
2. Description of the Prior Art
Polyamide, polyvinyl chloride, polypropylene, polyacrylic and polyester fibers are commonly used as materials for artificial and prosthetic hairs by either melt-spinning or wet-spinning methods, for example in dolls, wigs and hairpieces, or artificial hairs used for direct prosthetic implantation into human skin.
However, the fibers used as artificial hairs require certain characteristics, i.e., features peculiar to hair, such as color, strength, weathering resistance, as well as curling property, combing property, gloss peculiar to human hair, and the like.
Particularly as to gloss, man-made fibers generally have a brilliance similar to that of glass and hence, the direct use of these as artificial hair gives the immediate impression of an artificial substitute. Especially, under sunlight or spotlights, man-made fibers glisten dazzlingly with an unnatural gloss widely different from that of natural human hair. Therefore, many efforts have been made to produce a gloss similar to that of natural human hair, and this has usually been done by providing an unevenness on the surface of the fiber, or by incorporating a delustering (matting) agent into the fiber.
For example, there has been proposed a method for improving moisture absorption and gloss by spinning and fiberizing a mixture resulting from previous incorporation of an additive extractable with a solvent into a synthetic resin composition having a fiber-forming ability, and then extracting the additive with a solvent to form a large number of small voids in the surface of the resulting fiber (see Japanese Patent Publication No. 37649/72).
However, filaments produced by this method have a significantly reduced tensile strength because of the small voids formed in the surfaces thereof. Particularly, any diameter of the small void exceeding a required range will result in a failure to provide a satisfactory gloss and also in a considerably reduced strength. Therefore, such a fiber is not fit for use as an artificial hair. In addition, any length of the small void exceeding a required range will result in a considerably degraded appearance for an artificial hair. Moreover, the sizes of the small voids largely vary depending upon proportion of additive mixed, stretching condition, additive extracting condition and the like and hence, the control thereof is difficult, leading to a low yield and a low practical value. Further, from a medical viewpoint, the fiber having the additive and solvent remaining therein cannot be used as artificial hair for direct prosthetic implantation into the human skin, because such additives and solvents are toxic to the human body.
There has also been proposed a method for providing a gloss simulating that of the human hair by incorporating an inorganic delustering agent into a synthetic resin composition, and fiberizing the mixture to increase the coarseness in surface of the fiber, thereby moderating the gloss (see Japanese Patent Publication No. 46004/72 and Japanese Patent Application Laid-open No. 57116/74). However, an artificial hair produced by this method has disadvantages in that the tensile strength of the fiber itself is substantially reduced due to the flake-like crystalline inorganic delustering agent, and the combing property is degraded due to the delustering agent projecting from the filament surface. Further, the fiber produced by this method also cannot be used as an artificial hair for direct implantation into the human skin, because the additives and solvents remaining in the fiber are toxic to the human body.
In the course of researches for developing matted (delustered) artificial hairs, the present inventors have found a method for matting the fiber by providing a large number of lightly scrubbed scratches on the surface of monofilaments in the longitudinal direction of the fiber. This method can be easily carried out by putting a bundle of fibers between fabrics or sponges impregnated with an abrasive and then withdrawing the fiber bundle under light pressure in the longitudinal direction of the fiber. However, artificial hair produced using this method had certain disadvantages in that its appearance is still clearly different from natural human hair luster and if this artificial hair is curved somewhat by hand in a bundle, the resulting bent portion glistens extremely brightly and unnaturally, and particularly glistens dazzlingly under incandescent light or the direct rays of the sun and hence, this hair can be recognized as artificial on sight.